Method and apparatus for multiplexing in a wireless communication infrastructure

ABSTRACT

A network includes a plurality of antennas coupled to a plurality of base stations. The network can be optical or constructed with RF microwave links. The antennas and base stations are configured to transmit and receive digital signals representing cellular signals and the digital signals are exchanged over the network. A plurality of links couple the plurality of antennas and the plurality of base stations. At least one link of the plurality of links provides multiple transmission paths between at least a portion of the base stations and at least a portion of the antennas.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of U.S. Provisional ApplicationNo.: 60/296,781 filed Jun. 8, 2001 and U.S. Provisional Application No.:60/313,360 filed Aug. 17, 2001. This application is also acontinuation-in-part of U.S. Ser. No. 10/012,264 filed Nov. 5, 2001 anda continuation-in-part of U.S. Ser. No. 10/012,208 filed Nov. 5, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to cellular mobile telecommunicationsystems, and more particularly to a shared network to distribute basestation antenna points and the associated base station transceiverhardware.

2. Description of Related Art

A conventional cellular telecommunications system has a fixed number offrequency channel sets distributed among base stations that serve aplurality of cells that are usually arranged in a predetermined reusablepattern. Typical cell areas range from 1 to 300 square miles. The largercells can cover rural areas and smaller cells cover urban areas. Cellantenna sites utilizing the same channel sets are spaced by a sufficientdistance to assure that co-channel interference is held to an acceptablylow level.

A basic cellular network is comprised of mobile units, base stations,and a mobile switching center or mobile telecommunications switchingoffice (MTSO). The mobile unit has radio telephone transceiver equipmentthat communicates over a radio link with similar equipment in basestation sites. As the unit moves from cell to cell, communication withthe unit is handed off from one base station to another. Each basestation relays telephone signals between mobile units and an MTSO by wayof communication lines. The cell site and the MTSO are typicallyconnected by T1 lines, which carry telephone and control signals. TheMTSO is also connected through paths to a switched telephone network.

An MTSO can include a switching network for establishing callconnections between the public switched telephone network and mobileunits located in cell sites and for switching call connections from onecell site to another. Additionally, the MTSO can include control systemsfor use in switching a call connection from one cell site to another.Various handoff criteria are known in the art, such as using receivedsignal strength to indicate the potential desirability of a handoff.Also included in the MTSO is a central processing unit for processingdata received from the cell sites and supervisory signals obtained fromthe network to control the operation of setting up and taking down callconnections.

A conventional base station includes a radio controller unit thatprovides the interface between the T1 lines from the MTSO and the basestation radio equipment. It also includes one or more transceivers,which perform radio transmit and receive functionality, and are in turnconnected to antennas. A single transceiver radio often supports onechannel or frequency allocation. The focus of this invention lies inplacing a network between the transceiver radio and the antenna.Generally, the radio transmitter signals are then passed to a separatepower amplifier for each channel, or the signals may be combined andapplied to a single power amplifier. The output of the power amplifieris applied through a duplexer to an antenna, to be broadcast into thecellular area serviced by the base station.

Signals received in an antenna are applied through a duplexer to afilter. The filter isolates the entire cellular band signal fromadjacent bands and applies it to receivers, one for each channel. Thebase station may optionally include a diversity antenna andcorresponding diversity filters and a plurality of diversity receivers,one for each associated main receiver. Where implemented, the outputs ofdiversity receivers are applied to circuits include circuitry forselecting the strongest signal using known techniques. In denselypopulated urban areas, the capacity of a conventional system is limitedby the relatively small number of channels available in each cell.Moreover, the coverage of urban cellular phone systems is limited byblockage, attenuation and shadowing of the RF signals by high rises andother structures. This can also be a problem with respect to suburbanoffice buildings and complexes.

To increase capacity and coverage, a cell area can be subdivided andassigned frequencies reused in closer proximities at lower power levels.Subdivision can be accomplished by dividing the geographic territory ofa cell, or for example by assigning cells to buildings or floors withina building. While such “microcell” systems are a viable solution tocapacity and coverage problems, it can be difficult to find space at areasonable cost to install conventional base station equipment in eachmicrocell, especially in densely populated urban areas. Furthermore,maintaining a large number of base stations spread throughout a denselypopulated urban area can be time consuming and uneconomical.

A generic solution to this problem is to separate some components of thebase station from the antenna node, and connect them with a link. Thesmaller footprint antenna node is located at the desired coveragelocation, while the rest of the base station is placed at a moreaccessible location. The link is generally fiber optic. The related arthas approached this problem from two distinct positions: single linkfiber fed repeaters and distributed base station architectures. Fiberfed repeaters generally separate the base station at the radio output tothe antenna, employing a broadband transparent link which carries the RFuplink and downlink signals across the entire communication band, asdistinct from a single channel or frequency allocation (FA). Thebroadband link can be analog or digital, but if digital, the digitalsignal transparently repeats the entire band, for example, the 12.5 MHzUS Cellular A band. The link is point-to-point, one radio to oneantenna. Patents U.S. Pat. Nos. 5,627,879, 5,642,405, 5,644,622,5,657,374 and 5,852,651 form a group which teach the implementation ofcellular point-to-point links by employing a digital solutiontransparent to the communication protocol being employed.

The distributed base station solution, unlike the repeater solution,builds multi-link solutions. EP 0 391 597 discloses a simulcast networkover optical fiber using analog carriers. In the network envisioned bythis patent, multiple carriers are combined in the RF domain and thenoptically transported for simulcast transmission/reception out of afiber-fed antenna array. The optical carrier is analog modulated withthe RF signal. Dedicated fiber lines are used rather than opticallymultiplexed signals between remote antennas and the centralized basestation, and the signals are not multiplexed between multiple basestation radios and multiple antennas.

A distributed cellular network is disclosed in U.S. Pat. No. 5,519,691in which radios are pooled at a common location and communication linksconnect the radios to distributed antenna units. A multiplexing methodis provided for multiple channels on a cable or single optical carriernetwork, in which frequency division multiplexing in the RF domain iscombined with analog signal transmission. The network is closelyintegrated with the base station, with channel allocation andmanipulation at both host and remote ends of the network involving basestation control. Provision is also made for time division multiplexingin the signal domain.

Another distributed cellular network is disclosed in U.S. Pat. No.5,761,619. This network is closely integrated with the base stationarchitecture. The base station radios are placed at a different pointthan the antennas, and the radio is assumed to be a digital unit whicheither performs a wideband digitization of the cellular band orfiltering and a narrowband channel digitization. In this architecture,an optical network transports these digitized signals using a dynamicsynchronous protocol. In this protocol, circuit paths are dynamicallyset up between remote antenna nodes and base stations using thisprotocol. A synchronous TDM protocol is used for signal multiplexing.

U.S. Pat. No. 6,205,133 B1 discloses a digital architecture that issimilar to the one disclosed in U.S. Pat. No. 5,761,619. In thisdisclosed architecture, the concept of a software radio is used to builda distributed antenna system by modifying the base station architecture.The software radio transceivers are remotely located, and convert the RFsignals into digital signals, which are transported over a digital linkto a central hub station.

A distributed network architecture in which remote antenna units areconnected to a base center holding base station radios is disclosed inEP0368673/WO 90/05432. In this architecture, a fiber optic distributionnetwork is used to distribute RF signals between the base stations andthe antennas. An interconnect switch is used to connect RF signals fromdifferent radios onto different optical carriers, and these carriers arecombined and distributed by an optical fiber network. Analog RF opticalmodulation transmission is used but issues regarding constructing of atransparent ‘air link’ for carrying RF signals, which is required forcellular transmission, are ignored

U.S. Pat. No. 5,400,391 describes a similar architecture to that ofEP0368673, in which fiber pairs are used to connect distributed antennasto centralized radios, and an interconnection switch is used to flexiblydirect signals between antenna nodes and radio transceivers. Dedicatedfiber lines are used to connect base stations and remote nodes employinganalog RF modulation of the optical signals.

Further, U.S. Pat. Nos. 5,978,117 and 5,678,178 disclose networks usedto interconnect the base stations back to their respective MTSOs.

There is a need for a distributed network connecting base stations toremote antennas, and its method of use, that has a plurality of linkswith at least a portion providing multiple transmission paths. There isa further need for a distributed network connecting base stations toremote antennas, and its method of use, that has a plurality of linkswith at least one link providing multiple transmission paths employingmultiple optical wavelength multiplexing. There is yet another need fora distributed network connecting base stations to remote antennas, andits method of use, that has a plurality of links with cellular signalsare exchanged over the network are represented digitally. Yet there isanother need for a distributed network connecting base stations toremote antennas where at least one base station or antenna location isgeographically remote from the network and is connected to the networkwith a free space link. There is yet another need for a distributednetwork connecting base stations to remote antennas, that has aplurality of transmission paths that are shared between differentcellular operators.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide adistributed network that connects base stations to remote antennas, andits method of use, that has a plurality of links with at least a portionproviding multiple transmission paths.

Another object of the present invention is to provide a distributedoptical network connecting base stations to remote antennas, and itsmethod of use, that has a plurality of links with at least one linkproviding multiple transmission paths by employing multiple opticalwavelength multiplexing.

Yet another object of the present invention is to provide a distributednetwork connecting base stations to remote antennas, and its method ofuse, that has a plurality of links with cellular signals that areexchanged over the network and are represented digitally.

Another object of the present invention is to provide a distributedoptical network connecting base stations to remote antennas, and itsmethod of use, that has a plurality of links with at least one linkproviding multiple transmission paths by employing multiple opticalfiber strands.

A further object of the present invention is to provide a distributednetwork connecting base stations to remote antennas, and its method ofuse, where at least one base station or antenna location isgeographically remote from the network and is connected to the networkwith a free space link.

Another object of the present invention is to provide a distributednetwork, and its methods of use, that connects base stations to remoteantennas, and has a plurality of transmission paths that are sharedbetween different cellular operators.

Another object of the present invention is to provide a distributednetwork, and its methods of use, that connects base stations to remoteantennas, and has base stations co-located at a centralized location,and remote antennas distributed over a geographic area to providecellular coverage.

In one embodiment of the present invention, a network includes aplurality of antennas optically coupled to a plurality of base stations.The antennas and base stations are configured to transmit and receivedigital signals representing cellular signals and the digital signalsare exchanged over the network A plurality of links couple the pluralityof antennas and the plurality of base stations. At least one link of theplurality of links provides multiple transmission paths between at leasta portion of the base stations with at least a portion of the antennas.

In another embodiment of the present invention, a network includes aplurality of remote units and a plurality of base units. Each remoteunit is a radiating unit that has at least a portion of a functionalityof a base station. A plurality of links couple the plurality of remoteunits and the plurality of base units. At least one link of theplurality of links provides multiple transmission paths between at leasta portion of the base units with at least a portion of the plurality ofremote units.

In another embodiment of the present invention, a network includes aplurality of antennas optically coupled to a plurality of base stations.The base stations are configured to provide cellular transmission. Aplurality of links couple the plurality of antennas and the plurality ofbase stations. At least one link of the plurality of links providesmultiple transmission paths between at least a portion of the basestations with at least a portion of the antennas. At least a portion ofthe plurality of the links use fixed optical paths, wherein one node isconnected to another node over an optical path which is re-routedinfrequently compared to the bit rate of the communication protocolemployed over the path. In a preferred embodiment, a communication ornetworking protocol standard is employed over the fixed optical path. Ina preferred embodiment, this protocol can be Gigabit Ethernet, SONET,Fibre Channel, or ATM.

In another embodiment of the present invention, a network includes aplurality of antennas RF coupled to a plurality of base stations.Cellular signals exchanged over the network are represented digitally. Aplurality of links couple the plurality of antennas and the plurality ofbase stations. At least one link of the plurality of links providesmultiple transmission paths between at least a portion of the basestations with at least a portion of the antennas.

In another embodiment of the present invention, a method of transmissionprovides a network with a plurality of optical links that couple aplurality of antennas with a plurality of base stations. At least onelink provides multiple transmission paths using optical DWDM and digitaltransmission between at least a portion of the base stations with atleast a portion of the antennas.

In another embodiment of the present invention, a method of transmissionincludes providing a network with a plurality of links that couple aplurality of antennas with a plurality of base stations. Multipletransmission paths are provided between at least a portion of the basestations with at least a portion of the antennas. Signals are digitallytransmitted over the network.

In another embodiment of the present invention, a method of transmissionprovides a network with a plurality of optical links that couple aplurality of antennas with a plurality of base stations. At least onelink provides multiple transmission paths using optical DWDM between atleast a portion of the base stations with at least a portion of theantennas. Cellular signals are digitally exchanged over the network.

In another embodiment of the present invention, a method of transmissionprovides a network with a plurality of optical links that couple aplurality of antennas with a plurality of base stations. Multipletransmission paths are provided with at least one link using opticalDWDM between at least a portion of the base stations with at least aportion of the antennas. Digital signals representative of RF signalsbetween multiple base stations and antennas are carried by wavelengthcarriers. The digital signals are frequency down converted beforesampling and A/D conversion and frequency up converted after D/Aconversion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of one embodiment of a distributed basestation network with a plurality of antennas and base stations that hasmultiple transmission paths between at least a portion of the basestations with at least a portion of the antennas

FIG. 2 is a schematic diagram of a MEMs switch and Add/Drop Multiplexerthat can be used with the FIG. 1 network.

FIG. 3 is a schematic diagram of a SONET router that can be used withthe FIG. 1 network.

FIG. 4 is a schematic diagram of an optical multiplex/demultiplexer thatcan be used with the FIG. 1 network.

FIG. 5 is a schematic diagram of a DWDM transmission embodiment of theFIG. 1 network.

FIGS. 6a and 6 b are schematic diagrams of a point-to-point TDM topologyembodiment of the FIG. 1 network.

FIG. 7 is a schematic diagram of one fiber cable 20 with a plurality offiber strands which from the multiple transmission paths of the FIG. 1network.

FIG. 8 is a schematic diagram of a FIG. 1 network that uses free spaceoptical links.

FIG. 9 is a schematic diagram of a FIG. 1 network where at least aportion of the links are configured to provide a selectable allocationof capacity to at least some of the base stations.

FIG. 10 is a schematic diagram of a FIG. 1 network that multiple basestation 14 sites connected together.

FIGS. 11a and 11 b are schematic diagrams of a FIG. 1 network thatincludes a control box for at least a portion of the antennas in orderto provide routing to selected base stations.

FIG. 12 is a schematic diagram of a FIG. 1 network with amplifiersincluded in the links.

FIG. 13 is a schematic diagram of a FIG. 1 network that includes adigital transceiver embedded between a base station and the network on abase station side, and a digital transceiver embedded between an antennaand the network at an antenna side.

FIG. 14 is a schematic diagram of a FIG. 1 network illustratingtransmission of down link and up link signals.

FIG. 15 is a schematic diagram of a hub and spoke embodiment of the FIG.1 network.

FIG. 16 is a schematic diagram of a FIG. 1 network with at least twobase stations located in a common location and the antennasgeographically dispersed.

FIG. 17 is a schematic diagram of a FIG. 1 network with base stationsconnected together for different operators and used to extend coveragefrom each operator to other operators.

FIG. 18 is a schematic diagram of a FIG. 1 network that directlyconnects to an MTSO.

DETAILED DESCRIPTION

Referring to FIG. 1, one embodiment of the present invention is anetwork 10 that includes a plurality of antennas 12 that are opticallycoupled over network 10 to a plurality of base stations 14. Basestations 14 are configured to provide wireless cellular transmission. Aplurality of links 16 couple the plurality of antennas 12 and theplurality of base stations 14. At least one link 18 of the plurality oflinks 16 provides multiple transmission paths between at least a portionof the plurality of base stations 14 with at least a portion of theplurality of antennas 12. In one embodiment, the plurality of antennas12 and base stations 14 are coupled using RF links to form a network 10.By remotely locating the antenna 12 units from the base stations usingsuch a network 10, numerous advantages are realized.

The plurality of links 16 can be configured to provide multipletransmission paths by frequency division multiplexing (FDM), timedivision multiplexing (TDM), and the like. Optically coupled networkscan be configured to provide multiple transmission paths with wavelengthdivision multiplexing (WDM) and/or multiple fiber strands that comprisea fiber cable. Both of these optical multiplexing techniques allowelectrical isolation between different signals, because only the opticalfiber and multiplexing components need be shared, not electricalcomponents, optical transmitters, or optical receivers. TDM and FDM canboth be combined with WDM to increase the number of transmission pathsover a link. If the links 16 are RF microwave links, the multipletransmission paths can be different RF frequency channels.

Optical WDM also allows multiplexing of different signals with very lowlatency, because no processing or switching operation need be performed,low latency optical directing components can be used exclusively. Asillustrated in FIGS. 2, 3 and 4, optical multiplexing and routing can beperformed with low latency passive or switching components including,but not limited to a MEMS switch 18, Add/Drop Multiplexer 20, OpticalMultiplexer 24, and the like. Higher latency optical routing componentssuch as a SONET router 22 can be used as well, if the latency budget isacceptable. FDM can also have low latency because RF mixing andcombining are low latency operations, no processing or switching need beperformed. Low latency is a desirable property for the invention,because placing a network between the antenna 12 and current basestations 14 places strict latency limitations on the network 10, as thenetwork is now part of the conventional “air link” of a cellular system.This element of the link has strict latency constraints in moderncellular protocol standards, such as CDMA and GSM. However, other basestation 14 embodiments can compensate for greater latency in this “airlink” portion of the network 10, as it is a very small fraction of totallatency in a wireless call. Such base stations permit much more flexiblenetworking technology to be employed.

All or a portion of the links 16 can use optical FIG. 5 DWDM (DenseWavelength Division Multiplexing) for transmission. At least one link 16can provide multiple transmission paths employing digital transmissionsand DWDM multiplexing between at least a portion of the base stations 14with at least a portion of the antennas 12. DWDM ring networks also canemploy protection mechanisms, which can be important in theimplementation of this invention, because if a fiber link breaks,multiple cellular sites will go down. Such protection operates byrouting the optical signal in the opposite direction along the ring ifthere is a break. This routing can be accomplished by switching thedirection of transmission around the ring on detection of a break, or byalways transmitting optical signals between nodes in both directions,creating two paths for redundancy in case of a fiber break.

Some or all of the links 16 can use TDM (Time Division Multiplexing) tocreate the transmission paths. In one embodiment, the TDM employs SONETTDM techniques. In one embodiment, the TDM is specifically employed fromone node to another node on the network 10 to carry multiple distinct RFsignals in a point-to-point fashion. In a point-to-point TDM link,several signals are multiplexed together at an originating node, themultiplexed signal is then transported to the terminating node, and thenthe multiple signals are demultiplexed at the terminating node.Point-to-point TDM topology has the advantage of simplifying themultiplexing of multiple signals together, as opposed to adding anddropping low bit rate signals onto high bit rate carriers. Additionally,as illustrated in FIG. 6, the TDM link can carry multiple sectors of abase station 14. Further, the TDM link can carry multiple signals fromdifferent operators, carry diversity signals and be used to carrybackhaul signals.

All or a portion of the links 16 can employ the SONET protocol,particularly using fixed optical paths. In such an embodiment, the SONETprotocol is used to encode the signals, and then they are directed alongfixed optical paths in a multiple wavelength optical network 10. A fixedoptical path is one that is re-routed infrequently compared to the bitrate of the communication protocol employed over the path. This has theadvantage of simplifying routing, since now only wavelengths need berouted. In a more flexible network 10, more complex SONET routing can beemployed, for example, the links 16 can be multiplexed onto a SONETring. In such a routing scheme, the multiplexing involves routing bitsat the carrier bit rate of the ring, rather than routing opticalwavelengths.

Different optical wavelengths in a fixed or switched optical pathconfiguration can also employ other protocols. In one embodiment, atleast a portion of the links 16 employ Fibre Channel, Gigabit Ethernet,TCP, ATM or another transmission protocol. In one embodiment, at leastone optical wavelength carries OA&M signals and in another embodiment,at least one TDM channel carries OA&M signals.

Full SONET routing can be used over the network 10. In such a case, lowbit rate cellular signals are added and dropped off of higher bit rateSONET links, with flexible signal routing. SONET's low latency, TDMfunctionality, and wide availability for optical networkingimplementations make it a useful protocol for this application. In otherembodiments, IP routing is used. Routing protocols can be combined withtraffic data to route signals as needed to optimize capacity between agroup of base stations 14 and remote antenna 12 nodes.

As noted earlier, network 10 can provide optical multiplexing. In thisembodiment, the plurality of links 16 includes a plurality of opticalfiber links. As illustrated in FIG. 7, at least one fiber cable 20 canbe included with a plurality of fiber strands 22 which form the multipletransmission paths. For example, a 192 count fiber cable could be usedfor 192 fiber strands, allowing 192 signals to be multiplexed on thecable with no other form of multiplexing. Clearly, multiple cables canbe exploited in the same way as multiple strands. In another embodiment,at least one optical fiber strand 22 transmits at least two opticalwavelengths that form multiple transmission paths. Preferably, all ofthe optical fiber strands 22 transmit more than one optical wavelength.As an example, 6 strands could carry 32 wavelengths each, providing 192transmission paths. Beyond this, each path could have 4 signalsmultiplexed onto it employing TDM, providing 4×192=768 transmissionpaths.

Referring to FIG. 8, in other embodiments, the plurality of links 16 isa plurality of free space optical links 24. In such links, one or moreoptical wavelengths are directed through free space. Such links areuseful to employ in areas where fiber is expensive or unavailable. Theplurality of links 16 can include both optical fibers and free spaceoptical links 24.

At least a portion of the plurality of links can be configured toprovide selectable allocation of capacity to at least a portion of theplurality of base stations 14. This can be achieved with a controlswitching system 25. As illustrated in FIG. 9, such a system functionslike a switch, in which the RF traffic from the antennas 12 are directedinto it, and then redirected into base station 14 transceivers asneeded. The switch 25 also takes the downlink channels and distributesthem back to the antennas 12. The switch 25 can dynamically allocate thechannel capacity of a group of base station transceivers to antennas 12as needed. The capacity redirection switch 25 can be coordinated withthe RF channel allocation, in order that the same frequencies are notused adjacent to each other. The switch allows the base stationtransceiver capacity to serve the entire geographic region covered bythe antennas 12.

Referring to FIG. 10, a special case of shared base station transceivercapacity is to connect multiple existing base station 14 sites together,in order that the antennas 12 at these sites can be served by thetransceiver capacity of all the base stations 14. The statistics ofpooling transceiver capacity to cover larger geographic areas allowsfewer base stations 14 to be used than if they were individuallyconnected to single antennas. In addition, populations moving within thelarger geographic area are covered by the same transceiver pool, whichallows the number of transceivers to be sized with the population, notthe geographic coverage area. This reduces the number of base stations14 required to cover a given geographic area. In another embodimentshown in FIG. 11 a control box 27 can be included for each or a portionof the antennas 12 and provide routing to selected base stations 14. Therouting by the control boxes 27 can be performed according to a desiredschedule. For example, the switch could allocate more channels tohighways during commute hours, and more channels to commercial officeparks during business hours. One or all of the plurality of the links 16can include a passive optical device 26. Suitable passive opticaldevices 26 include but are not limited to OADM's, filters, interleavers,multiplexers, and the like.

All of only a portion of the plurality of links 16 can include one ormore optical amplifiers 28, FIG. 12. Optical amplifiers 28 are lowlatency devices that amplify optical signals, overcoming optical lossesfrom fiber and the use of optical components. Such amplifiers 28 arecommercially available in configurations that amplify blocks ofwavelengths, which makes DWDM optical networking more feasible,especially given the optical losses sustained in wavelengthmultiplexing.

The cellular signals exchanged over network 10 can be analog signals ordigitized. Analog signals generally involve modulating a laser oroptical modulator with the cellular RF signal, or a frequency convertedversion of this signal. Such implementations have the advantage ofsimplicity, and can take advantage of WDM, multiple fiber strands 22 ona given fiber cable 20, and FDM. However, for such transmission, thechannel properties of the link 16, such as noise figure and spur-freedynamic range, directly impact the signal properties. DWDM networksexperience linear and non-linear crosstalk, causing signal interferencebetween different wavelength carriers. This can create problems withanalog RF transmission. Digital signals are streams of bits, generatedby digitally encoding the analog cellular signal. The analog cellularsignal is the signal that would normally be transmitted or received bythe base station or the remote mobile units. So a PCS CDMA signal couldbe an “analog cellular signal.” It is not meant to imply that the signalis representative of an analog cellular standard. If the digitalrepresentation of the analog cellular signal is transmitted with asufficient signal-to-noise ratio, it will not be significantly affectedby link properties. Furthermore, these digital signals can be digitallyprotected with various strategies, such as encoding, parity, etc., tofurther reduce the likelihood of bit errors. By employing digitalsignals, there is a significant improvement in resistance to crosstalk.Hence DWDM and digital transmission is a powerful combination forexploiting the network 10 to carry the maximum number of cellularsignals. Digital signals are furthermore amenable to the use of digitalcommunications equipment and standards, such as routers, IP and SONET.

In one embodiment, the wavelength carriers carry an analog signalrepresentative that is representative of an RF signal between multiplebase stations 14 and antennas 12. Different carriers carry differentcellular signals. In another embodiment, the wavelength carriers carry adigital signal that is representative of an RF signal between multiplebase stations 14 and antennas 12. This digitization can be implementedin two preferred embodiments.

As illustrated in FIG. 13, a digital transceiver 30 is embedded betweenthe base station 14 and the network 10 on the base station 14 side, andbetween the antenna 12 and the network 10 at the antenna 12 side. Thecoupling can be either a direct connection, or through one or more RFcomponents such as an amplifier, attenuator, gain control block, and thelike. The analog cellular signal, which is normally exchanged betweenthese two units, is first converted into a digital signal by the digitaltransceiver, which is then exchanged over the network 10. After thedigital cellular signal is received at the other end of the network, itis reconstituted by the digital transceiver as an analog cellularsignal. This signal can be filtered, amplified, attenuated, and the likebefore being transmitted to the antenna 12, or the base station 14.

The other embodiment is to integrate the digital component into the basestation 14 unit and the antenna 12 unit, and not use a separate digitaltransceiver. Although this can involve digitizing a wireless channel orfrequency band, a more sophisticated implementation is to separate thefunctionality of the base station 14 unit and the antenna 12 unit at apoint where the signal is itself digital. Given that the cellular RFsignal is a digitally modulated signal, the voice channel is digitized,and base stations 14 are migrating to a digital transmit/receivearchitecture, there are several intermediate digital signals that couldbe exchanged. The antenna 12 units, when serving as remote units, canprovide conventional base station 14 functionality such as basebandcoding, channel coding, modulation/demodulation, channel filtering, bandfiltering and transmission reception and the like.

The general case is that each antenna 12 location can be configured toreceive a downlink cellular signal as a digital stream input that isrepresentative of a single or multiplicity of wireless channels or asegment of wireless spectrum. The antenna 12 then reconstructs andtransmits the RF signal. Additionally, uplink cellular signals arereceived off-air at the antenna 12 that are representative of a singleor a multiplicity of wireless channels from at least one mobile unit. Atthe antenna 12 node the uplink cellular signal is then converted into asingle or plurality of bit streams. The bit streams are then transmittedover the network 10 to the base station 14 units. The base station 14units receive this uplink digital signal and process it. Additionally,they transmit a downlink digital signal to the network 10.

When digital transceiver units are used to perform D/A and A/Dfunctionality between antennas 12 and base stations 14, the analogsignals can be frequency down converted before sampling and A/Dconversion, and frequency up converted after D/A conversion. The digitalsignal can be serialized before transmission and converted back to aparallel signal after transmission. High bit rates, including but notlimited to those greater than 500 Mbps, can be employed to create highdynamic range links for improved cellular performance.

Referring to FIG. 14, when digital transceivers are employed, at thebase station, the digital transceivers 30 digitize the downlink analogcellular signals that are representative of a wireless spectrum band orchannel. Thereafter, the digital transceivers 30 pass the downlinkdigital cellular signals to the network 10. For the uplink at the basestation, the digital transceivers 30 receive uplink digital signalsrepresentative of a wireless spectrum band or channel from the network,reconstruct the analog cellular signals, and then pass them to the basestations 14. At the antennas 12, for the uplink, the analog cellularsignals received on the antenna 12 from the mobile units are convertedinto digital signals, and transmitted onto the network 10. The downlinkdigital signals are received by digital transceivers at the antenna 12,and then converted back into analog cellular signals representative of awireless spectrum band or channel, and passed to the antenna 12.

In various embodiments, network 10 can have different layouts. In oneembodiment, at least a portion of the plurality of the links 16 arefixed optical paths. Such paths involve connecting one or more remotenodes to one or more base nodes and rarely dynamically re-routing thispath. The optical paths between antennas 12 and base stations 14 canhave a one-to-one correspondence, connecting to one antenna 12 node andone base station 14 unit, or alternatively, one or more antennas 12 canbe connected to one or more base stations 14 in a non one-to-oneembodiment. In another embodiment, the transmission paths of network 10can be dynamic-routable optical paths flexibly routed between one or aplurality of base stations 14 and one or a plurality of antennas 12.

As illustrated in FIG. 15, network 10 can be configured as a hub andspoke network 32. In this embodiment, the plurality of base stations 14are located in a common node 34 and the plurality of antennas 12 arelocated at different remote nodes, generally denoted as 36 on thenetwork 32. Optical uplink and downlink connections are spokes 38 thatconnect the common node 34 and the remote nodes 36. Network 32 can alsoinclude at least one set of nodes 40 containing the base stations 14and/or antennas 12 which are connected by one or more links 16 that arelaid out on a segment or a ring. Whether on a segment or a ring, in apreferred implementation the uplink and downlink should be transmittedin opposite directions to equalize the latency, which is important incellular transmission.

In one embodiment, at least two of the base stations 14 are located in acommon location and the antennas 12 are geographically dispersed, FIG.16. Suitable common locations include but are not limited to anenvironmentally controlled room in a building connected to the network10. The antennas 12 are placed in areas providing the desired coveragewhich may have higher real estate costs and/or lower availablefootprints than the common location, but which can be connected to thenetwork 10.

In various embodiments, at least one link of the plurality of links 16can be, shared by at least two operators. The operators can be wirelessoperators, different spectrum bands used by a same cellular operator,different entities. This different operators need not share electricalcomponents when using an optical network. Different operators can bemultiplexed onto the network using any of the multiplex methods detailedpreviously. In a preferred implementation, the different operators canuse different optical fibers strands, or different optical wavelengthson the same fiber strand. In another preferred implementation, differentoperators can employ different wavelengths on free space links. Byoptically multiplexing multiple operators on the same network 10, theoperators can share the costs of constructing, acquiring and maintainingthe network 10 without compromising their electrical isolationrequirements. In one embodiment, the network 10 can be used to connecttogether existing base station 14 sites for different operators, andused to extend coverage from one operator to all other operators.

For example, as illustrated in FIG. 17, a site built by operator A atsite A is connected to a site built by operator B at site B. An antenna12 for A is placed at site B, connected to a base station 14 foroperator A at site A, and an antenna 12 for operator B is placed at siteA, connected to a base station 14 for operator B at site B.

In various embodiments, the links 16 provide that at least one opticalcarrier carries at least one backhaul signal from a base station 14 to aswitch (such as an MTSO) or a bridge network. In an RF network, wherethe links 16 are RF links, the links 16 can be configured to providethat at least one RF carrier carries at least one backhaul signal from abase station 14 to one of a switch (such as an MTSO) or a bridgenetwork.

Referring now to FIG. 18, the network 10 can be an optical network thatdirectly connects to a switch 42, including but not limited to an MTSO.Multiple backhaul signals from several base stations can be integratedinto one higher bit rate backhaul signal. This allows the network 10costs to be shared amongst backhaul signals as well, and allows for highbandwidth backhaul to be performed, which is cheaper per bit. Thebackhaul signals can be digital t-carriers, SONET signals, and the like.Non-backhaul RF signals that share the network 10 with the backhaulsignal can be represented digitally to minimize the effects of crosstalkwith the digital backhaul signal. Non-backhaul RF signals can have alarge wavelength separation from the backhaul signal in order tominimize the effects of crosstalk with the digital backhaul signal.

Some antenna 12 or base station 14 locations are difficult to connect toa network, especially an optical fiber network, because no fiber mayexist to the site. In an embodiment of the invention, such a locationcan be connected to the network 10 with a free space link, either a freespace optical link 16 or microwave link 16. This link 16 can be analogor digital, and if digital can be formatted in a proprietary fashion, oras a T-carrier or SONET link.

The foregoing description of preferred embodiments of the invention hasbeen presented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formsdisclosed. Obviously, many modifications and variations will be apparentto practitioners skilled in this art. It is intended that the scope ofthe invention be defined by the following claims and their equivalents.

What is claimed is:
 1. A network, comprising: a plurality of antennasoptically coupled over the network to a plurality of base transceiverstations, wherein the antennas and base stations are configured totransmit and receive signals representing cellular signals and thesignals are exchanged over the network; and a plurality of links thatcouple the plurality of antennas and the plurality of base transceiverstations, at least one multiple transmission path link of the pluralityof links providing multiple transmission paths between at least aportion of the base stations with at least a portion of the antennas, atleast one transmission path configured to carry all spectrum of aselected bandwidth; and at least one capacity redirection switch coupledto the at least one multiple transmission path link to one of theantennas, the antennas directing RF traffic into the at least onecapacity redirection switch which then redirects RF traffic into basetransceiver stations as needed.
 2. The network of claim 1, wherein theoptical links are optical fiber links.
 3. The network of claim 2,wherein the plurality of links are configured to provide that at leastone fiber link carries at least one backhaul signal from a basetransceiver station of the plurality of base transceiver stations to aswitch or a bridge network.
 4. The network of claim 2, wherein at leastone of the links is configured to transmit at least two opticalwavelengths to create at least a portion of the multiple transmissionpaths.
 5. The network of claim 4, wherein the plurality of links areconfigured to provide that at least one optical wavelength carriercarries at least one backhaul signal from a base transceiver station ofthe plurality of base stations to a switch or a bridge network.
 6. Thenetwork of claim 1, wherein the optical links are free space opticallinks.
 7. The network of claim 6, wherein at least one of the links isconfigured to transmit at least two optical wavelengths to create atleast a portion of the multiple transmission paths.
 8. The network ofclaim 1, wherein at least one of the links is configured to transmit atleast two optical wavelengths to create at least a portion of themultiple transmission paths.
 9. The network of claim 8, wherein theplurality of links are configured to provide that at least one opticalwavelength carrier carries at least one backhaul signal from a basestation of the plurality of base stations to a switch or a bridgenetwork.
 10. The network of claim 8, wherein additional transmissionpaths are created using frequency division multiplexing on the opticalcarriers.
 11. The network of claim 1, wherein at least one of the linksis configured to use time division multiplexing to create at least aportion of the multiple transmission paths.
 12. The network of claim 11,wherein the plurality of links are configured to provide that at leastone TDM channel carries at least one backhaul signal from a basetransceiver station of the plurality of base stations to a switch or abridge network.
 13. The network of claim 2, wherein at least one of thelinks is configured to use time division multiplexing to create at leasta portion of the multiple transmission paths.
 14. The network of claim13, wherein the plurality of links are configured to provide that atleast one TDM channel carries at least one backhaul signal from a basetransceiver station of the plurality of base transceiver stations to aswitch or a bridge network.
 15. The network of claim 6, wherein at leastone of the links is configured to use time division multiplexing tocreate at least a portion of the multiple transmission paths.
 16. Thenetwork of claim 15, wherein the plurality of links are configured toprovide that at least one TDM channel carries at least one backhaulsignal from a base transceiver station of the plurality of base stationsto a switch or a bridge network.
 17. The network of claim 1, whereinwavelength division multiplexing and time division multiplexing incombination creates at least a portion of the multiple transmissionpaths.
 18. The network of claim 17, wherein the plurality of links areconfigured to provide that at least one TDM channel and/or opticalwavelength carrier carries at least one backhaul signal from a basetransceiver station of the plurality of base stations to a switch or abridge network.
 19. The network of claim 2, wherein wavelength divisionmultiplexing and time division multiplexing in combination creates atleast a portion of the multiple transmission paths.
 20. The network ofclaim 19, wherein the plurality of links are configured to provide thatat least one TDM channel and/or optical wavelength carrier carries atleast one backhaul signal from a base transceiver station of theplurality of base transceiver stations to a switch or a bridge network.21. The network of claim 6, wherein wavelength division multiplexing andtime division multiplexing in combination creates at least a portion ofthe multiple transmission paths.
 22. The network of claim 12, whereinthe plurality of links are configured to provide that at least one TDMchannel and/or optical wavelength carrier carries at least one backhaulsignal from a base transceiver station of the plurality of base stationsto a switch or a bridge network.
 23. The network of claim 1, furthercomprising: a plurality of digital transceivers coupled to the pluralityof antennas and base stations that generate digital signals.
 24. Thenetwork of claim 23, wherein at least one of a digital transceiver ispositioned at a base station and digitizes a downlink analog cellularsignal generated by the base station that is representative of awireless spectrum band and transmits it to one or more antennas over thenetwork.
 25. The network of claim 24, wherein the digital transceiver atthe base transceiver station receives an uplink digital signalrepresentative of a wireless spectrum band from an antenna over thenetwork and reconstructs the analog cellular signal to pass to the basetransceiver station.
 26. The network of claim 25, wherein a digitaltransceiver at an antenna digitizes an uplink cellular signal receivedfrom the antenna and transmits a digital signal to one or more basetransceiver stations over the network.
 27. The network of claim 26,wherein the digital transceiver positioned at the antenna receives adigital signal representative of a downlink wireless spectrum band froma base station over the network and reconstructs the downlink analogsignal to transmit to one or more mobile wireless units.
 28. A network,comprising: a plurality of remote units and a plurality of base units,wherein each of a remote unit is a radiating unit that has at least aportion of the functionality of a base transceiver station; and aplurality of links coupling the plurality of remote units and theplurality of base units, at least one link of the plurality of linksproviding multiple transmission paths between at least a portion of thebase units with at least a portion of the plurality of remote units, atleast one transmission path configured to carry all spectrum of aselected bandwidth; and at least one switching device coupled by one ofthe links to one of the antennas.
 29. The network of claim 28, whereineach of a remote unit of the plurality of remote units provides basebandcoding.
 30. The network of claim 28, wherein each of a remote unit ofthe plurality of remote units provides channel coding.
 31. The networkof claim 28, wherein each of a remote unit of the plurality of remoteunits provides modulation and demodulation.
 32. The network of claim 28,wherein each of a remote unit of the plurality of remote units provideschannel filtering.
 33. The network of claim 28, wherein each of a remoteunit of the plurality of remote units provides band filtering.
 34. Thenetwork of claim 28, wherein each of a remote unit of the plurality ofremote units provides transmission and reception.
 35. The network ofclaim 28, where the each of a remote unit of the plurality of remoteunits provides the transmit chain from modulation to transmission, andthe receive chain from reception to demodulation.
 36. The network ofclaim 28, wherein the plurality of links are free space links and thetransmission paths employ different wavelength optical carriers.
 37. Thenetwork of claim 28 wherein the plurality of links are a plurality of RFlinks and the transmission paths employ different frequency RF carriers.38. The network of claim 28, wherein the plurality of links are opticalfiber links.
 39. The network of claim 38, wherein the transmission pathsemploy different wavelength optical carriers.
 40. The network of claim28, wherein at least a portion of the plurality of radiating units areantennas.
 41. The network of claim 40, wherein at least of the portionof the plurality of base units are base transceiver stations.
 42. Thenetwork of claim 28, wherein each of a remote unit is configured toreceive a digital stream downlink from a base unit over the network thatis representative of a downlink wireless spectrum band, construct ananalog cellular signal from the digital stream and transmit the analogcellular signal to one or a plurality of wireless mobile units.
 43. Thenetwork of claim 42, wherein each of a remote unit is configured toreceive an off-air analog cellular signal representative of an uplinkwireless spectrum band, create an uplink digital stream and thentransmit the uplink digital stream to a base unit over the network. 44.The network of claim 43, wherein the digital stream downlink is producedby at least one a base unit of the plurality of base units and theuplink digital stream is received by at least one of a base unit of theplurality of base units.
 45. The network of claim 28, wherein each of aremote unit of the plurality of remote units is configured to receive adigital signal input that is representative of one or more wirelesschannels, convert the digital signal to an analog cellular signal andthen transmit the analog cellular signal to one or more mobile wirelessunits.
 46. The network of claim 45, wherein each of a remote unit isconfigured to receive an analog cellular signal representative of one ormore wireless channels from at least one mobile wireless unit, convertthe analog cellular signal into one or more digital Signals, andtransmit the one or more digital signals to at least one base unit overthe network.
 47. A network, comprising: a plurality of antennasoptically coupled over the network to a plurality of base transceiverstations, the base transceiver stations configured to provide cellulartransmission; a plurality of links that couple the plurality of antennasand the plurality of base transceiver stations, at least one link of theplurality of links providing multiple transmission paths between atleast a portion of the base transceiver stations with at least a portionof the antennas, at least a portion of the plurality of links beingfixed optical paths, wherein each of a fixed optical path is astationary optical link between one or more base transceiver stationsand one or more antennas that is rerouted on a time scale much slowerthan that of the bit rate over the link, and so connects nodes to oneanother as a virtual circuit, at least one transmission path configuredto carry all spectrum of a selected bandwidth; and at least oneswitching device coupled by one of the links to one of the antennas. 48.The network of claim 47, in which a networking or communication protocolstandard is employed over the fixed optical path.
 49. The network ofclaim 48 where the protocol standard is selected from Gigabit Ethernet,Fibre Channel, SONET, T-carrier, ATM, and TCP.
 50. A network,comprising: a plurality of antennas RF coupled over the network to aplurality of base transceiver stations, wherein the antennas and basetransceiver stations are configured to transmit and receive signalsrepresenting cellular signals, and wherein the signals are exchangedover the network; a plurality of links that couple the plurality ofantennas and the plurality of base transceiver stations, at least onelink of the plurality of links providing multiple transmission pathsbetween at least a portion of the base stations with at least a portionof the antennas, at least one transmission path configured to carry allspectrum of a selected bandwidth; and at least one switching devicecoupled by one of the links to one of the antennas.
 51. The network ofclaim 50, wherein time division multiplexing creates at least a portionof the multiple transmission paths.
 52. The network of claim 51, whereinthe plurality of links are configured to provide that at least one TDMchannel carries at least one backhaul signal from a base transceiverstation of the plurality of base transceiver stations to a switch or abridge network.
 53. The network of claim 50, wherein different frequencychannels create at least a portion of the multiple transmission paths.54. The network of claim 53, wherein the plurality of links areconfigured to provide that at least one FDM channel carries at least onebackhaul signal from a base station of the plurality of base transceiverstations to a switch or a bridge network.
 55. A method of transmission,comprising: providing a network that includes a plurality of opticallinks that couple a plurality of antennas with a plurality of basetransceiver stations and at least one switching device; providingmultiple transmission paths with at least one link using optical DWDMbetween at least a portion of the base transceiver stations with atleast a portion of the antennas; encoding signals over the multipletransmission paths; using the switch to allocate at least one wavelengthfrom the link to the one of the antennas while passing all otherwavelengths to another switching device; and at least one transmissionpath configured to carry all spectrum of a selected bandwidth.
 56. Themethod of claim 55, wherein at least one transmission path carries OA&Msignals.
 57. The method of claim 55, wherein at least a portion of theplurality of the links include a plurality of fixed optical paths,wherein each of a fixed optical path is a stationary optical linkbetween one or more base stations and one or more antennas that isrerouted on a time scale much slower than that of the bit rate over thelink, and so connects nodes to one another as a virtual circuit.
 58. Themethod of claim 57, in which a networking or communication protocolstandard is employed over the fixed optical path.
 59. The method ofclaim 58 where the protocol standard is selected from Gigabit Ethernet,Fibre Channel, SONET, T-carrier, ATM, and TCP.
 60. The method of claim55, wherein at least a portion of the plurality of links are multiplexedonto at least one SONET ring.
 61. The method of claim 55, wherein atleast a portion of the plurality of the links transmit using the SONETprotocol.
 62. The method of claim 61, further comprising: providingSONET protection against a failure in the network.
 63. The method ofclaim 62, wherein the failure is a break in a fiber link.
 64. The methodof claim 62, wherein the failure is a failure of equipment in thenetwork.
 65. A method of transmission, comprising: providing a networkthat includes a plurality of links that couple a plurality of antennaswith a plurality of base transceiver stations and at least one switchingdevice; providing multiple transmission paths between at least a portionof the base transceiver stations with at least a portion of the antennasby at least one link of the plurality of links; encoding signals overthe multiple transmission paths digitally; using the switch to allocateat least one wavelength from the link to the one of the antennas whilepassing all other wavelengths to another switching device; and at leastone transmission path configured to carry all spectrum of a selectedbandwidth.
 66. The method of claim 65, wherein a digital signal isserialized before transmission and converted back to a parallel signalafter transmission.
 67. The method of claim 65, wherein one or aplurality of optical amplifiers amplifies a digital signal in theplurality of links.
 68. The method of claim 65, wherein bit ratesgreater than 500 Mbps are employed to create high dynamic range linksfor improved cellular performance.
 69. The method of claim 65, whereinSONET routing is used over the network.
 70. The method of claim 65,wherein IP routing is used over the network.
 71. The method of claim 65,wherein routing protocols are combined with traffic data to routesignals to optimize capacity for a group of base stations and remoteantenna nodes.
 72. The method of claim 65, wherein digitallytransmitting signals over the plurality of transmission paths reduceseffects of crosstalk between the multiple transmission paths.
 73. Themethod of claim 65, wherein at least a portion of the plurality ofantennas receive uplink analog cellular signals from one or more mobilecellular units, sample the analog signals, generate a digital streamrepresenting the analog cellular signals, and transmit the digitalstream to one or more base stations over the network.
 74. The method ofclaim 73, wherein at least a portion of the plurality of base stationsreceive uplink digital signals from one or more antennas over thenetwork.
 75. The method of claim 65, wherein at least a portion of theplurality of base stations create a digital signal representing thedownlink cellular signal and then transmit the digital signal to one ormore antennas over the network.
 76. The method of claim 75, wherein atleast a portion of the plurality of antennas receive downlink digitalsignals from one or more base transceiver stations over the network,convert the digital signals to analog cellular signals, and transmitsthose cellular signals to one or more mobile wireless units.
 77. Themethod of claim 65, wherein at least a portion of the plurality of linksuse TDM to create transmission paths.
 78. The method of claim 77,wherein the TDM uses SONET TDM techniques.
 79. The method of claim 77,wherein the TDM is employed to carry multiple distinct cellular signalsfrom one node to another node, in which all of the multiple signals aremultiplexed together at an originating node, the multiplexed signal isthen transported to a terminating node, and then the multiple signalsare demultiplexed at the terminating node.
 80. The method of claim 79,wherein the TDM is employed to carry multiple sectors of a basetransceiver station system.
 81. The method of claim 79, wherein TDM isemployed to carry multiple signals from different operators.
 82. Themethod of claim 79 wherein the TDM is performed with SONET or T-carriersignals.
 83. The method of claim 79 wherein the TDM is performed tocarry diversity signals.
 84. The method of claim 79 wherein the TDM isperformed to carry backhaul signals.
 85. The method of claim 65, whereinsampling and digitizing a wireless spectrum band generates a digitalsignal.
 86. The method of claim 85, wherein the base station samples anddigitizes the downlink analog cellular signal, and transmits a digitalsignal to one or more antennas over the network.
 87. The network methodof claim 86, wherein the antenna samples and digitizes an uplinkcellular signal received from a wireless mobile unit and transmits adigital signal to one or more base transceiver stations over thenetwork.
 88. The method of claim 86, wherein the antenna receives thedigital signal representative of a downlink wireless spectrum band froma base transceiver station over the network and reconstructs thedownlink analog signal to transmit to one or more mobile cellular units.89. The method of claim 87, wherein the base station receives an uplinkdigital signal representative of one or more wireless spectrum band froman antenna over the network.